Polyelectrolyte Trilayer Combinations Using Spin-Assembly and Ionic Self-Assembly

Water-soluble, cationic, anionic, and neutral polymers are used to form various repeat trilayer films via ionic self-assembly (ISA) and spin-assembly. These multilayer thin films assemble through physical entanglement, electrostatic, and/or H-bonding interactions. Spin assembly has the advantage over ISA in constructing stable multilayers when polyelectrolytes with like charge are assembled in adjacent layers. These multilayers do not desorb in water over a long period of time. In contrast to spin assembly, the ISA method deposits only a minimal amount of polyelectrolyte on top of a like-charged layer. The mechanical entanglement that is responsible for the deposition of like-charged species in spin assembly is probably lacking in ISA. The ability to construct repeated trilayers or multilayers composed of polycations, polyanions, and neutral polymers allows the fabrication of multilayer thin films with the desired interfacial structure and interactions. In this work, polyelectrolytes with NLO chromophores are used because the deposition can be easily monitored through UV−visible spectroscopy and they have potential utility for NLO thin film devices. The adsorption kinetics of an ISA trilayer was studied, and it was found that the adsorption reaches equilibrium in 15 s to 5 min, depending on the structure and specific interaction between layers.